The embodiments presented in this disclosure generally relate to Lithographic printing and more particularly to imaging of wet Lithographic printing plates and pre-press handling of inkjet imaged wet Lithographic printing plates.
Lithographic printing is based on the principle that oil and water do not mix. A lithographic printing plate has non-image areas which absorb water (hydrophilic areas) and image areas which repel water (hydrophobic areas). For a wet offset lithographic printing, the plate is first dampened water so that the ink is applied to the wetted printing plate to form the image. The ink, which is inherently oily, is rejected by the wet areas and adheres to the image areas. The ink from the inked printing plate is then transferred or “offset” to a rubber blanket. Next, the image on the blanket is transferred to the substrate to produce the printed product.
Common polyester wet lithographic plates have hydrophilic top layer that is formed by organic hydrophilic polymer and inorganic particles of micron and submicron sizes. Usually such layer has relative low thickness: some printing plate with organic hydrophilic layer, such as polyester silver plates, have hydrophilic layer with a thickness under 2-3 micron. A common imaging process of a polyester wet lithographic plates having relative low thickness hydrophilic top layer, involves unhealthy chemicals and expensive imaging devices, such as computer-to-plate (CTP) devices.